Hexamethyldisilazane

Hexamethyldisilazane (HMDS) is most commonly used as a blocking agent to protect hydroxyl groups in naturally occurring or semisynthetic compounds; for example, cephalosporins and prostaglandins. The trimethylsilyl derivative prevents chemical reactions at the protected site, allowing other functionalities to be modified. Deprotection by mild acids or bases regenerates the original hydroxyl functionality. The major advantage in the use of HMDS for blocking is that both the blocking and deblocking reactions give high yields.